Test multiple Rubies on CI

Author: odlp

.github/workflows/main.yml

@@ -1,17 +1,18 @@
 ---
-on:
-  pull_request:
-  push:
-    branches:
-      - master
+on: [push]
 
 jobs:
   test:
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: [2.7, 2.6, 2.5]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: ruby/setup-ruby@v1
         with:
+          ruby-version: ${{ matrix.ruby }}
           bundler-cache: true
       - name: Test
         run: bundle exec rspec